Is mixing and matching Covishield, Covaxin safe? Study provides BIG update

A total of 330 volunteers, who were not vaccinated and had no history of the COVID-19 infection, were selected and screened for SARS-CoV-2 antibodies for the study.

Dr D Nageshwar Reddy, Chairman, AIG Hospitals (second from left) along with researchers involved in the study

New Delhi: A Hyderabad-based hospital has conducted a pilot study to determine the safety profile of mixing two COVID-19 vaccines namely Covishield and Covaxin.

The study conducted by AIG Hospitals along with researchers from the Asian Healthcare Foundation showed that mixing Covishield and Covaxin is 'absolutely safe and there are no adverse effects' on any of the participants.

A total of 330 healthy volunteers, who were not vaccinated and had no history of the COVID-19 infection, were selected and screened for SARS-CoV-2 antibodies for the study. Out of these, 44 (13%) participants were found to be seronegative, ie, they didn't have the COVID-related antibodies.

“One of the incidental findings of the study is the seropositivity among our population. 87% of participants who didn’t get vaccinated and never tested positive for COVID-19 had COVID-related antibodies. This means our population might have developed significant antibodies against the COVID-19 because of the huge Delta wave that we endured,” said Dr D Nageshwar Reddy, Chairman, AIG Hospitals. 

India, like many other countries, is currently seeing the trend of the third wave fuelled by the Omicron variant. Although the initial data indicates that this wave will be milder than the Delta one with less hospitalization, still a large section of the population might get affected, according to the researchers.

As the Union Government has approved “Prevention” vaccine doses for the healthcare workers, elderly, and the vulnerable population, it is important to find out the cross-immunity generated by mixing of the available vaccines. It is also crucial that the safety profiles are well-established before administrating different vaccines as prevention or booster doses, the researchers added.

STUDY MODEL AND DETAILS

44 participants were divided into two four groups.

Group 1: First Dose of Covishield + Second Dose of Covishield 

Group 2: First Dose of Covaxin + Second Dose of Covaxin

Group 1 and 2 were the homologous vaccine groups in which same vaccine have been given and relevant antibody titers were checked.

Group 3: First Dose of Covishield + Second Dose of Covaxin

Group 4: First Dose of Covaxin + Second Dose of Covishield

Group 3 and 4 were the heterogeneous vaccine groups in which different vaccines were given and antibody titers were checked. All these 44 participants were followed for 60 days to see if there’re any adverse effects.

The study conclusively found that mixing vaccines are absolutely safe as none of the participants developed any adverse effect. The most important finding of the study was that the Spike-protein neutralizing antibodies found in the mixed vaccine groups were significantly higher than the same-vaccine groups. 

"Spike-protein neutralizing antibodies are the ones which kill the virus and reduce the overall infectivity. We found that when the first and second doses are of different vaccines, the Spike-protein antibody response is four times higher compared to two-dose of the same vaccine,” Dr Reddy said.

“This is particularly important when considering the third booster dose. The concept of a booster is to elicit a robust antibody response and help in killing the virus. Mixed doses can certainly boost these Spikeprotein neutralizing antibodies and will enhance the vaccines’ effectiveness even against the Omicron variant,” he added.

The study results show that mixing of Covishield and Covaxin provide a higher antibody response and is safe as well.

The AIG Hospitals has shared the data from the study with the Indian Council for Medical Research (ICMR) to be considered as a reference study while deciding on the “Prevention” doses starting January 10.